MACHINE  SHOP  NOTES, 


PAKT  I. 


FOR    THE    USE   OF  STUDENTS  IN  SHOP  WORK. 


itesadntsetts;  Institute  of 


BY 

It.    II.    SMITH. 


COPYRIGHT,  1888,  BY  K.  II.  SMITH. 


BOSTON: 

PRINTED  BY  J.  S.  (TSIIING  &  CO. 
1888. 


MACHINE  SHOP  NOTES, 


PART  I. 


FOR   THE   USE   OF  STUDENTS  IN  SHOP  WORK. 


Institute  of 


BY 

R.    H.    SMITH. 


COPTBIGHT,  1888,  BY  R.  H.  SMITH. 


BOSTON: 
PRINTED  BY  J.  S.  GUSHING  &  CO. 

1888. 


Stacf 

Annex 

5017834 


i-s « 

3  tc  e 
fc-S  § 


0—3 
»-  ->   » 

O     t-   T3 


.    be 
£    o 


o    o 

rj      o 


—     "^      ° 

O  £  P5 


H    ;§ 
^    1 


v  f3    01 

,;    a    Pi  M 

o  i  o  ^ 


O 


»S  3 
W  H 


MACHINE  SHOP  NOTES, 


GENEKAL  BISECTIONS, 

1.  Each   student   will   be   given   a  lathe   and   check   number ;   the 
former  designates  the  lathe   he  will  use  during  his  course,   and  the 
latter  his  shop  number  or  number  of  his  tool  box.     The  lathe  number 
is  placed  on  the  left-hand  corner  of  the  lathe. 

2.  Lathe   Cupboard.  —  Each  engine  lathe    cupboard    contains  the 
following  tools :  A  12"  scale,  3"  scale,  centre  gauge,  large  and  small 
outside   calipers,   inside   calipers,    stop   for   thread   cutting,   drift   pin 
for  removing  live  centre,  two  small  parallel  blocks  (used  when  boring), 
wrenches  for  lathe,  change  gears  for  screw  cutting,  and  (for  all  Putnam 
lathes)  a  stud  used  when  cutting  left-hand  threads. 

3.  Tool  Box.  —  Each  tool  box  contains  a  right-hand  diamond  point, 
a  right-hand  side,  and  a  round-nosed  tool,  a  monkey-wrench,  a  centre 
punch,  a  scratch  awl,  a  small  oil  stone,  some  chalk,  and  five  checks 
on  a  ring,  each  having  the  same  number  as  the  tool  box. 

The  tool  boxes  are  kept  in  the  tool  room,  there  being  one  for  each 
student,  marked  clearly  with  his  shop  number  and  used  only  by  him. 

4.  Beginning  Work.  —  On  giving  his  shop  number  to  the  attendant 
at  the  tool  room  window,  the  student  will  receive  his  tool  box  at  the 
beginning  of  each  exercise. 

Before  beginning  work,  each  student  should  examine  his  lathe  cup- 
board and  tool  box  to  see  if  ever}Tthing  is  in  place  ;  should  anything 
be  lacking,  report  it  at  once  to  the  instructor  in  charge.  A  failure 
to  do  this  will  make  the  student  responsible  for  anything  found  missing 
at  the  close  of  the  exercise. 

5.  Use  of  Checks.  —  Each  of  the  five  checks  is  numbered  the  same 
as  the  tool  box,  and  they  should  be  used  for  extra  tools  taken  from  the 
tool  room,  one  check  being  deposited  for  each  tool  taken  out.     Tools 
obtained  by  check  should  be  returned,  well  cleaned,  immediately  after 
having  finished  using   them,  the   deposited   checks  being   received   in 
exchange  for  the  tools.     Students  will  be  held  responsible  for  the  loss 


6  MACHINE   SHOP   NOTES. 

or  breakage  of  any  tool  while  it  is  in  their  charge.  In  asking  for  a 
tool  at  the  tool  room,  be  sure  and  state  clearly  what  you  wish  to  use 
it  for. 

6.  Closing  Work.  —  At  the  close  of  each  exercise  return  all  bor- 
rowed tools  and  the  tool  box  with  everything  in  its  place.     Stamp  your 
work  plainly,  whether  it  be  finished  or  unfinished,  and  put  it  in  the 
pigeon  hole  of   the  work   case   having  your  shop  number.     See  that 
everything  about  the  machine  you  have  been  using  is  in  proper  place, 
and  thoroughly  clean  the  machine  with  brush  and  waste.     The  brush 
may  be  found  on  the  outside  of  the   lathe  cupboard,  and  waste  may 
be  obtained  at  the  tool  room.     All  oily  waste  is  to  be  thrown  into  a 
sheet-iron  box  provided  for  it.     In  putting  away  work,  be  sure  and  oil 
the  finished  surfaces  to  prevent  their  rusting. 

7.  Oil  Cans. — The  nickel-plated  oil  cans,  on  brackets  in  different 
parts  of   the  shop,  contain  machine  oil  which  is  only  to  be  used  for 
lubricating  purposes ;  those  found  at  each  lathe  contain  lard  oil  to  be 
used  for  various  purposes,   such  as  drilling,  tapping,   screw   cutting, 
polishing,  etc.,  but  not  for  oiling  machinery. 

8.  Machinery.  —  Before  using  any  machine,  the   student  should 
understand  its  general  construction  in  order  that  he  may  intelligently 
use  it  and   avoid   accidents.      If  at   any  time  in   doubt,  the  student 
should  question  the  instructor. 

Before  starting,  see  that  the  machine  is  well  oiled,  and  that  the 
moving  parts  are  free ;  the  latter  can  usually  be  determined  by  moving 
the  driving  belt  by  hand. 

9.  Drawings. — Drawings  of  all  pieces  are  kept  in  the  toolroom, 
where  they  may  be  obtained  when  wanted. 

10.  Stock.  —  On  receiving  a  piece  of  rough  stock,  see  that  it  will 
finish  to  the  dimensions  given  on  the  drawing,  or  that  it  is  of  such  size 
that,  when  turned  or  planed  to  within  ^"  of  finish  size,  all  the  skin  will 
be  removed  from  the  finished  parts.      Should  the  stock  not  be  large 
enough  to  finish  to  dimensions,  or  should  there  be  any  flaw  in  it,  report 
at  once  to  the  instructor. 

When  possible,  remove  the  skin  from  all  finished  parts  of  a  piece 
before  finishing ;  except  in  squaring  the  ends  of  turned  work,  where  the 
piece  may  be  finished,  as  to  length,  before  removing  the  skin  from  the 
cylindrical  surface. 

ENGINE  LATHE. 

11.  Most  of  the  engine  lathes  in  the  machine  shop  have  eight  speeds, 
—  four  with  the  back  gears  in,  and  four  with  the  gears  out.     They  are 
all  screw  cutting,  and  are  supplied  with  hand  and  power  longitudinal 


ENGINE   LATHE.  7 

feed.     All  have  hand  cross  feed ;  and  some  have  both  hand  and  power 
cross  feed. 

Those  lathes  supplied  with  a  belt  feed  have  only  three  changes,  by 
means  of  step  pulleys.  Those  supplied  with  gear  feed  may  have  any 
range  of  feed  within  the  combinations  of  the  change  gears.  For  a  fine 
feed,  place  a  small  driving  gear  on  the  "  stud,"  or  spindle,  and  a  large 
following  gear  on  the  splined  "lead  screw";  an  intermediate  gear,  or 
idler,  being  arranged  between  them,  to  communicate  motion  from  one 
to  the  other.  To  increase  the  feed,  put  a  larger  gear  on  the  stud. 
Care  should  be  taken  in  setting  these  gears,  so  that  the  teeth  will  mesh 
properly. 

12.  Lathe  Centres. — The  "centres"  are  classed  among  the  most 
particular  parts  of  a  lathe,  as  upon  their  truth  depends  that  of  all  work 
done  upon  them.     It  is  therefore  essential  that  they  be  kept  in  good 
order  and  perfectly  true.     The  centre  in  the  headstock  spindle,  or  head 
spindle,  is  called  the  live  centre,  and  the  one  in  the  tailstock  spindle,  or 
tail  spindle,  the  dead  centre. 

Each  live  centre  has  a  line  on  its  shank  parallel  with  its  axis ;  to 
insure  that  the  centre  shall  always  be  put  back  in  the  same  position 
relative  to  the  spindle,  when  removed,  this  line  is  made  to  intersect 
another  line  drawn  on  the  end  of  the  live  spindle. 

To  test  the  truth  of  the  live  centre,  move  the  tailstock  up  the  lathe 
bed  until  the  dead  centre  is  close  to  the  live  centre,  run  the  lathe  at  its 
highest  speed ;  the  eye  can  then  quickly  perceive  whether  the  live  centre 
runs  true  or  not.  This  is  also  an  approximate  method  for  setting  the 
dead  centre  in  line  with  the  live  centre. 

Lathe  centres  and  centre-reamers,  or  countersinks,  are  made  to  fit 
the  60°  centre  gauge  (A,  Fig.  3),  found  in  the  lathe  cupboard.  This 
insures  ample  bearing  of  the  centred  piece  ;  thus  preventing  undue  wear, 
and  preserving  the  truth  of  the  centres. 

It  is  not  absolutely  necessary  that  the  live  centre  be  perfectly  true 
when  "squaring  up  "  or  "  roughing  out"  work;  but  it  should  be  per- 
fectly true  when  taking  a  finishing  cut.  In  any  case,  it  is  best  to  have 
the  centre  true. 

The  dead  centre  :s  usually  hardened  ;  the  live  centre  may  or  may  not 
be  hardened,  usually  not. 

TETJING  CENTKES, 

13.  Remove  the  dead  centre,  by  running  the  spindle  back  in  the  tail- 
stock  until  the  screw  pushes  the  centre  out ;  then  anneal,  by  heating  it 
to  a  cherry  red  and  allowing  it  to  cool  slowly.     Remove  the  live  centre 
by  a  drift  pin,  which  can  be  found  in  the  lathe  cupboard.     (In  lathes 
which  have  hollow  spindles,  the  live  centre  has  to  be  driven  out  with  a 


8  MACHINE   SHOP   NOTES. 

rod,  which  can  be  found  at  the  side  of  the  lathe.)  Great  care  should 
be  taken  to  properly  clean  the  shank  of  the  centre  and  the  hole  in  the 
spindle.  Place  the  dead  centre  in  the  headstock  spindle ;  then,  with  a 
centre  tool  (a  broad-nosed  tool,  employed  for  this  purpose  only),  turn 
it  to  fit  the  centre  gauge. 

The  cutting  edge  of  the  tool  should  be  at  the  same  height  as  the 
line  of  centres. 

The  live  centre  is  trued  in  the  same  manner  as  the  dead  centre. 

File  the  dead  centre  a  very  little  with  a  "  dead  smooth"  file,  harden, 
and  draw  to  a  straw  color,  but  do  not  file  or  harden  the  live  centre. 

14.  Centre-Grinding  Machine.  — To  operate  upon  hardened  centres, 
a  centre-grinding  machine  is  employed ;  a  driving  wheel  is  bolted  to  the 
lathe  face  plate ;  a  stand,  set  over  the  tool  post  and  held  in  place  by 
the  set  screw,  carries  at  its  top  the  overhead  belt  pulleys,  and  at  its 
base  the  emery  wheel  and  spindle.     A  feed  lever  is  pivoted  on  the  end 
of  the  emery  wheel  spindle,  by  means  of  which  the  emery  wheel  may  be 
traversed  along  the  lathe  centre.     By  the  use  of  this  machine  the  dead 
centre  may  be  trued  up  without  having  to  anneal  it. 

15.  Setting  Centres  on  Line.  —  To  have  a  lathe  turn  perfectly  straight, 
the  centres  must  be  on  line.     If  the  dead  centre  has  been  set  over  to 
turn  taper,  and  it  be  desired  to  set  it  to  turn  straight  again,  place  a 
cylindrical  bar  that  is  true  on  the   centres ;    adjust  a  pointed  tool  to 
make  a  light  mark  on  the  end  of  the  bar  (next  to  the  live  centre)  when 
the  carriage  is  traversed ;  then,  without  moving  the  cross  feed,  take  the 
bar  out  of  the  lathe,  and  run  the  carriage  until  the  tool  is  near  the  dead 
centre ;  put  the  bar  in  the  lathe  again  with  the  marked  end  next  to  the 
dead  centre.     The  tool  should  now  leave,  when  traversed,   a  similar 
mark  on  the  bar. 

It  consumes  a  vast  amount  of  time  to  go  through  this  operation 
every  time  it  is  required  to  set  a  lathe  to  turn  straight.  To  save  this 
time,  two  zero  lines  are  put  on  the  rear  end  of  the  tailstock.  "When 
these  lines  coincide,  the  lathe  will  turn  practically  straight.  The  "  Brown 
&  Sharpe  "  and  "  Pratt  &  Whitney"  lathes  will  turn  straight  when  the 
sides  of  the  tailstock  are  flush.  Always  unclamp  the  tailstock  before 
moving  the  adjusting  screws  ;  do  not  bring  these  screws  up  hard,  but  just 
enough  to  prevent  any  side  movement  of  the  spindle. 

In  Fig.  1  is  shown  a  device  for  setting  the  tailstock  of  a  lathe  to 
turn  parallel  work.  A  is  a  bar  of  cast  iron  about  £' '  square,  its  length 
being  about  the  radius  of  the  face  plate  of  the  lathe.  B  is  a  small  hole 
drilled  through  A  and  countersunk  at  C  and  D,  as  shown  (in  the  figure. 
E  is  an  adjusting  screw  supplied  with  a  divided  circle  at  F,  and  an 
index  bar  at  G,  which  enables  settings  to  be  readily  made. 

The  method  of  using  the  above  device  is  as  follows  :  Move  the  tail- 


SPEED   LATHE. 


9 


stock  up  the  lathe  bed  near  the  live  centre  and  adjust  the  dead  centre 
approximately.     Place  the  countersink  C  on  the  live  centre,  and  D  on 


© 


B 


D 


the  dead  centre,  and  clamp  both  tailstock  and  spindle.  Turn  the  screw 
E  in,  by  means  of  the  thumb  screw,  until  it  will  just  touch  the  face  plate, 
and  notice  its  reading.  Now  turn  the  screw  back  about  one  revolution. 
Then  turn  the  live  spindle  and  the  device  one-half  a  revolution,  and> 
again  turn  the  screw  in  until  it  will  just  touch  the  face  plate  :  if  it  reads 
the  same  as  before,  the  tailstock  is  right,  and  the  lathe  will  turn  parallel ; 
but  if  it  does  not,  the  tailstock  must  be  adjusted  until  the  same  reading 
is  obtained  on  opposite  sides. 

To  get  good  results  with  the  foregoing  or  any  device,  the  live  centre 
must  be  perfectly  true. 

SPEED  LATHE. 

16.  The  speed  lathe,  or  hand  lathe,  is  a  high-speed  machine  without 
automatic  feeds,  usually  arranged  with  four  changes  of  speed,  and  is 
used  for  drilling,  turning  on  centres,  chuck  turning,  chucking,  and  polish- 
ing. These  lathes  are  fitted  with  slide  rests,  T  rests,  chucks  of  various 
sizes,  drill  rests,  drill  sockets,  chucking  tools,  slide  rest  tools,  etc. 
Tools  not  at  the  lathe  can  be  procured  at  the  tool  room. 

By  the  use  of  this  lathe  small  work  of  any  kind  can  be  turned, 
chucked,  or  faced,  without  the  aid  of  an  engine  lathe,  and  with  greater 
rapidity. 

This  lathe  is  also  very  useful  for  small  drilling,  polishing,  and  brass 
work,  on  account  of  its  high  speed. 

Hand  tools  are  used  in  connection  with  the  slide-rest  tools  for  round 
ing  edges  and  ends  and  turning  irregular  forms. 

The  centres  are  similar  to  those  of  an  engine  lathe,  and  are  trued  up 
with  a  hand  tool  called  the  "  graver." 


10  MACHINE   SHOP   NOTES. 

It  is  well  to  remember  that  work  revolving  at  a  high  speed  should 
be  kept  free  on  the  centres,  and  that  the  dead  centre  should  be  fre- 
quently oiled.  As  work  gets  warm,  it  will  expand  and  bind  on  the 
centres,  and  if  you  are  not  watchful,  will  twist  off  the  point  of  the  dead 
centre,  thus  spoiling  both  work  and  centre.  This  is  also  liable  to  hap- 
pen on  an  engine  lathe. 

CUTTING  TOOLS. 

17.  Lathe  and  planer  cutting  tools  are  usually  made  of  a  grade  of 
cast  steel  known  as  "tool  steel";  they  are  forged,  filed  up  to  the  re- 
quired form,  and  then  hardened  and  tempered. 

An  outside  tool  is  employed  on  external,  and  an  inside  tool  on  in- 
ternal, surfaces. 

A  right-hand  tool  will  cut  from  right  to  left,  a  left-hand  tool  from 
left  to  right. 


Fig.  2. 

Fig.  2  represents  a  right-hand  diamond  point  tool ;  A  is  termed  the 
top  face ;  its  inclination  in  the  direction  of  the  arrow  13  is  its  front,  and 
its  inclination  in  the  direction  of  the  arrow  C  its  side  rake,  these  angles 
being  considered  with  relation  to  the  bottom  plane  of  the  tool  FF.  The 
angle  of  the  bottom  edge  or  face  E  with  the  line  FD  is  the  clearance  or 
the  bottom  rake. 

It  is  well  to  remember  that  nearly  all  the  keenness  should  be  placed 
on  the  top  face  of  a  tool ;  the  office  of  the  bottom  face  is  to  support  the 
cutting  edge ;  therefore  the  amount  of  clearance,  or  bottom  rake,  should 
only  be  sufficient  to  make  the  tool  clear  well  and  not  ride  on  the  work. 

It  is  obvious  that  various  combinations  of  front  and  side  rake  may 
be  given  to  a  tool ;  for  heavy,  deep  cuts,  a  maximum  of  side  rake  may 
be  used  to  advantage  ;  and  for  finishing,  a  maximum  of  front  rake. 

For  small  work,  where  the  cuts  are  not  heavy  and  the  tool  is  em- 
ployed for  both  roughing  out  and  finishing,  it  is  an  advantage  to  give 
the  top  face  of  the  tool  a  combination  of  front  and  side  rake  of  about 
equal  proportions. 

Tools  employed  on  machinery  steel  or  wrought  iron  should  have  top 
rake  enough  to  make  them  keen ;  for  cast  steel  or  any  hard  metal  the 


SPEED   AND   FEED   FOR   LATHES.  11 

rake  should  be  reduced  so  that  the  tool  will  stand  a  reasonable  time 
without  regrinding.  Tools  with  top  rake  can  be  employed  to  advantage 
on  cast  iron  ;  but  if  the  metal  is  hard,  the  amount  must  be  small. 

The  difference  between  tools  employed  on  iron  and  steel,  and  those 
employed  on  brass,  is,  that  the  latter  do  not  require  any  top  rake  ; 
for  if  too  keen,  they  will  chatter,  thus  giving  the  surface  of  the  brass 
a  mottled  appearance. 

To  farther  illustrate  the  foregoing,  a  complete  set  of  lathe  and  planer 
tools  is  kept  in  the  tool  room.  Each  tool  is  ground  to  the  angles  suit- 
able for  the  purpose  for  which  it  is  designed  ;  that  is,  to  angles  that  have 
been  found  by  experience  to  give  good  results.  These  tools  are  to  be 
used  as  models,  and  the  student  can  occasionally  compare  his  tools  with 
them. 

When  grinding  a  toot,  hold  it  firmly  in  the  hands,  this  being  the  only 
•way  to  get  good  results.  It  is  not  always  desirable  to  bear  hard  on 
the  grindstone  or  emery  wheel,  since  too  great  pressure  on  the  stone,  or 
especially  on  the  emery  wheel,  will  cause  the  tool  to  become  heated  so 
as  to  draw  its  temper. 

18.  Holding  Tools. — A  tool  should  be  so  fastened  that  its  cutting 
edge  is  as  near  the  tool  post  as  circumstances  will  permit,  the  object 
being  to  avoid  its  springing  and  to  prevent  as  far  as  possible  its  giving 
way  to  the  cut. 

SPEED  AND   PEED  FOE  LATHES. 

19.  Cutting  speed  as  applied  to  machine  tools  means  the  number 
of  feet  of  cutting  performed  by  the  tool  in  a  given  time. 

Feed  as  applied  to  machine  tools  means  the  thickness  of  the  shaving 
taken  by  the  tool,  measured  in  the  direction  of  the  feed. 

There  is  no  part  of  machine-tool  work  in  which  a  greater  variation  is 
possible  than  in  the  speed  and  feed  of  lathe  work  ;  for  what  would  be 
coarse  feed  on  one  piece  of  work  might  be  fine  on  another ;  and  what 
would  be  high  speed  on  one  piece  might  be  slow  on  another ;  therefore, 
we  cannot  lay  down  definite  rules  in  all  cases,  as  the  nature  of  the 
work  may  render  peculiar  conditions  of  speed  and  feed  necessary  ;  how- 
ever, enough  will  be  said  in  what  follows,  and  in  connection  with  each 
class  of  work,  to  form  a  basis  which  will  enable  the  student  to  determine 
for  himself  what  speed  and  feed  is  the  most  advantageous. 

The  speed  and  feed  of  a  lathe  should  be  varied  according  to  the 
nature  of  the  material  to  be  turned.  In  turning  heavy  work,  time  is 
saved  by  running  slowly  and  using  a  coarse  feed  ;  on  small  work,  by 
running  at  as  high  a  speed  as  the  tool  will  stand  and  using  a  fine  feed. 

If  the  material  is  heavy  wrought  iron,  steel,  or  cast  iron,  use  slow 
speed  and  coarse  feed;  but  if  the  work  is  hard,  reduce  the  speed  and 
feed  so  that  the  tool  will  stand  a  reasonable  time  without  regfrinding. 


12  MACHINE   SHOP  NOTES. 

If  the  work  is  light  and  liable  to  spring,  use  fast  speed  and  fine  feed. 

On  brass,  run  at  a  high  rate  of  speed,  unless  it  is  very  hard,  and 
always  use  fine  feed. 

In  boring  or  inside  turning  an  advantage  is  gained  by  running  at 
a  reasonable  speed,  and  feeding  fine,  as  there  is  always  more  or  less 
spring  in  all  boring  tools. 

20.  Houghing  out  work  is  taking  off  one  or  more  cuts  which  reduce 
it  to  within  about  ^¥"  of  finished  size. 

If  the  cut  is  very  heavy,  the  tool  is  liable  to  draw  in  as  it  advances, 
thus  turning  the  work  to  a  smaller  diameter  than  that  it  Avas  set  for. 
In  turning  long  and  slender  pieces  which  would  be  liable  to  spring  from 
the  pressure  of  the  tool,  a  steady  rest  or  back  rest  is  employed  to  sup- 
port the  work. 

In  the  roughing  cut,  the  object  is  to  remove  the  surplus  metal  as 
quickly  as  possible,  and  prepare  the  work  for  the  finishing  cut ;  there- 
fore, the  tool  should  be  set  to  turn  off  all  the  surplus  metal  whenever 
the  lathe  has  power  enough  to  drive  the  cut;  and  the  cutting  speed 
should  be  as  fast  as  the  depth  of  the  cut  and  tool  will  permit. 

Both  for  roughing  and  finishing  cuts  it  is  advisable  to  have  the  feed 
as  coarse  as  the  conditions  will  allow. 

21.  In  taking  the  roughing  cut  there  is  no  objection  to  removing 
the  tool  to  regrind  it,  but  in  the  case  of  the  finishing  cut  it  is  desirable 
that  the  tool  carry  the  cut  its  full  length  without  regrinding,  because  of 
the  difficulty  of  again  setting  the  tool  to  cut  to  exact  diameter. 

OENTKING. 

22.  Place  the  work  in  a  vise ;  chip  or  file  the  snags  off,  and  rub 
chalk  on  the  ends  :  next  open  a  pair  of  dividers  (compass  calipers  are 
more  convenient)  to  a  distance  approximately  equal  to  the  radius  of  the 
work,  and  hold  one  leg  firmly  against  the  perimeter  of   the  work,  as 
near  the  end  as  possible,  while  with  the  point  of  the  other  leg  a  line  is 
marked  on  the  end  of  the  work  ;  perform  this  operation  at  four  equi- 
distant points.     If  the  dividers  are  opened  more  or  less  than  the  radius 
of  the  work,  a  small  space  will  be  enclosed  between  these  lines ;  the  eye 
can  now  quickly  and  easily  locate  its  centre,  where  the   centre  punch 
may  be  placed,  and  a  light  hammer  blow  produces  the  required  inden- 
tation. 

Next  place  the  work  between  the  lathe  centres  and  revolve  it  to  see 
if  it  is  true  enough  to  turn  to  size  ;  if  so,  make  a  deep  indentation  with 
the  centre  punch  to  guide  the  drill. 

If  the  work  does  not  run  true  enough  to  turn  to  size,  revolve  it  with 
one  hand,  and  hold  a  piece  of  chalk  with  the  other  (allowing  the  hand 


CENTEING.  13 

to  rest  on  some  part  of  the  machine) ,  so  that  the  most  eccentric  part  of 
the  work  will  touch  the  chalk ;  with  the  hammer  and  centre  punch  set 
the  hole  over  toward  where  the  chalk  has  touched  the  work  ;  repeat  this 
operation  until  the  work  runs  true  enough. 

23.  Centre   Drilling.  —  Centre  drill   with  the  speed   lathe,  running 
the  belt  on  the  third  speed  when  using  a  centre  drill  of  about  Ty  in 
diameter.     By  the  third  speed  is  meant  that  when  the  belt   is  on  the 
third  step  from  the  right-hand  end  of  the  cone. 

The  centre  drill  is  revolved  by  the  live  spindle,  and  held  in  either  a 
small  chuck  or  socket. 

Place  one  end  of  the  work  on  the  dead  centre  and  support  the  other 
end  with  the  left  hand  on  a  line  with  the  centre  drill ;  with  the  right 
hand  screw  out  the  tailstock  spindle.  The  work  will  then  be  forced 
upon  the  revolving  drill,  thus  drilling  the  hole. 

Be  careful  in  drilling  to  allow  no  weight  to  rest  upon  the  drill ;  if  oil 
is  needed,  the  drill  should  be  freely  supplied,  using  the  right  hand  for 
that  purpose. 

Always  use  oil  in  drilling  and  countersinking  steel,  wrought  iron, 
and  brass  ;  but  never  use  oil  on  cast  iron. 

It  is  very  important  during  this  operation  of  drilling  to  screw  the 
tailstock  spindle  back  about  two-thirds  of  the  depth  of  the  hole  every 
few  seconds,  the  object  being  to  let  the  chips  get  out  of  the  hole  and 
the  oil  get  in.  This  method  renders  the  drill  less  liable  to  be  broken 
in  the  hole,  it  often  being  a  very  difficult  operation  to  remove  from  the 
hole  the  piece  of  the  drill  thus  broken. 

In  screwing  the  tailstock  spindle  back,  be  sure  and  press  the  work 
hard  against  the  dead  centre  with  the  left  hand,  so  that  it  will  not  fall 
off  and  spring  or  break  the  drill. 

24.  Countersinking. — The  countersink  should  have  the  same  angle 
as  the  lathe  centres. 

To  countersink,  run  the  lathe  at  the  first  speed,  and  hold  the  work  as 
in  centre  drilling,  relaxing  every  few  seconds  the  hold  upon  the  work 
sufficiently  to  let  it  make  about  a  quarter  revolution,  the  object  being  to 
make  the  centre  hole  true. 

In  countersinking,  the  point  of  the  countersink  must  not  be  allowed 
to  touch  the  bottom  of  the  drilled  hole,  as  such  contact  will  break  the 
point,  and  also  change  the  angle  of  the  hole.  It  must  also  be  remem- 
bered that  the  centres  of  all  lathe  work  should  be  cleared  at  the  bottom, 
so  that  the  extreme  points  of  the  lathe  centres  will  not  touch  the  work 
and  be  injured.  Therefore,  always  drill  the  hole  about  \"  below  the 
countersink.  The  size  of  the  centre  holes  depends  on  the  *uze  of  the 
finished  work  and  on  the  cutting  pressure  of  the  lathe  tools. 

Work  finishing  1"  or  under  should  have  centre  holes  not  larger  than 


14  MACHINE   SHOP  NOTES. 

£"  outside  diameter  when  squared  to  length;  that  finishing  1"  and  1£" 
should  have  the  diameters  -fa"  and  \"  respectively.  For  work  finishing 
between  these  sizes,  and  larger,  judgment  should  be  used,  taking  into 
account  the  appearance  of  the  work  and  the  pressure  on  the  lathe  centres. 
After  the  student  is  familiar  with  the  above  process  of  centring,  the 
centring  machine  can  be  used. 

25.  The  centring  machine  is  employed  to  centre  and  centre-drill  at 
one  operation,  doing  the  work  much  quicker  than  can  be  done  by  hand. 
The  chuck  is  universal,  the  jaws  moving  simultaneously.     After  care- 
fully centring,  drilling,  and  countersinking,  we  come  to  the  squaring 
of  the  ends. 

PLACING  WORK  ON  CENTRES. 

26.  With  a  piece  of  waste  wipe  the  centre  holes  and  centres.     This 
must  be  remembered ;  for  if  any  chips  or  grit  are  left  on  the  centres  or  in 
the  centre  holes,  the  work  will  run  out  of  true. 

Fasten  a  "  dog"  on  one  end  of  the  work,  the  tail  of  the  "  dog"  project- 
ing over  the  end  far  enough  to  catch  in  the  slot  in  the  face  plate  of  the 
lathe. 

Place  the  end  with  the  "  dog  "  attached  on  the  live  centre  ;  with  the  left 
hand  under  the  other  end,  press  the  work  against  the  live  centre  to  pre- 
vent it  from  falling  off,  and  hold  it  on  a  line  with  the  dead  centre, 
allowing  the  little  finger  to  project  by  the  end  to  guide  the  centre  into 
the  hole ;  with  the  right  hand  slide  the  tailstock  to  position,  and  clamp 
it,  leaving  space  enough  to  work  the  slide  rest  freely  for  squaring  the 
end.  Always  put  oil  on  the  dead  centre  or  in  the  centre  hole,  and  never 
allow  the  centre  to  become  dry ;  then  gently  screw  out  the  tailstock 
spindle  until  there  is  no  end  movement  to  the  work,  and  clamp  the 
spindle. 

A  very  common  method  of  determining  whether  work  is  tight  on  the 
centres  or  not  is  to  judge  by  the  force  required  to  partially  rotate  it. 
Be  very  careful  not  to  get  the  work  tight  on  centres.  "When  taking  a 
heavy  cut  the  work  will  get  warm  and  expand,  and  thus  bind  on  the 
centres  ;  therefore,  the  student  should  be  watchful,  and  under  such  con- 
ditions should  relieve  and  oil  the  dead  centre  quite  frequently.  If  this 
is  neglected,  it  is  liable  to  cause  the  destruction  of  both  work  and  centre. 

SQUARING  CAST  IRON. -CARD  101-A, 

27.  Always  "  square  up  "  the  ends  of  the  work  to  the  length  that  is 
specified  on  the  drawing  before  turning  off  the  cylindrical  surface. 

For  squaring  up  work,  set  the  point  of  the  tool  at  the  same  height  as 
the  point  of  the  centres. 

To  remove  the  skin  on  the  end,  a  small  round-nosed  tool  is  employed, 


STRAIGHT   TURNING,   CAST   IRON.  15 

j.nd  the  cut  is  carried  from  circumference  to  centre  ;  then  a  side  tool  is 
employed  with  a  top  rake  of  about  20°.  Set  the  cutting  edge  of  the 
tool  at  an  angle  of  about  10°  with  the  end  of  the  work,  so  that  it  will 
cut  deepest  at  the  point,  enabling  it  to  carry  a  cut  from  centre  to  cir- 
cumference. To  square  up  the  opposite  end,  reverse  the  work  in  the 
lathe. 

Rough  out  both  ends,  leaving  the  piece  -fa"  longer  than  the  given 
length.  Before  taking  the  finishing  cut  on  the  ends,  see  that  the  centre 
holes  are  right  and  of  uniform  size  (for  Card  101  they  should  be  about 
T3^-"  in  diameter),  as  they  should  not  be  countersunk  after  the  work  is 
squared  to  length.  The  ends  of  the  work  should  be  flat ;  test  them  with 
the  edge  of  a  scale. 

Before  taking  the  finishing  cut  on  any  piece  of  work,  see  that  the  tool 
has  a  sharp  edge. 

Speed  for  Squaring.  —  Card  101-A.  —  For  the  roughing  cuts  use  the 
second  speed,  and  for  the  finishing  cut,  the  third  speed,  "  back  gears 
out." 

STRAIGHT  TUENDJG,  OAST  IKOU.-OAKD  101-A. 

28.  For  parallel  work  the  lathe  centres  must  stand  on  the  same  line. 
In  order  to  turn  a  piece  of  work  from  end  to  end,  it  is  necessary  to 

reverse  it  in  the  lathe.  Always  place  a  piece  of  copper  or  brass  under 
the  set-screw  of  the  "dog"  on  turned  work. 

Select  a  right-hand  diamond-point  tool,  with  a  top  rake  of  about  20°, 
and  the  point  slightly  rounded  ;  set  the  shank  of  the  tool  at  about  right 
angles  to  the  work,  and  the  point  above  the  centre  sufficiently  to  make 
it  cut  well,  but  not  enough  to  allow  the  bottom  face  of  the  tool  to  rub 
against  the  work. 

Set  the  calipers  fa"  larger  than  the  given  diameter,  and  turn  the 
work  to  that  size  with  one  roughing  cut,  provided  the  lathe  will  carry 
it ;  if  it  will  not,  take  two  roughing  cuts,  or  more  if  necessary.  For 
the  finishing  cut,  grind  the  tool,  a,nd  round  its  point  a  little  more  ;  then 
set  the  calipers  to  the  given  diameter,  and  proceed  as  on  the  roughing  cut. 

In  taking  a  finishing  cut,  the  tool  should  cany  its  cut  the  full  length 
of  the  work  without  regrinding,  because  of  the  difficulty  of  resetting 
the  tool  to  cut  to  the  exact  diameter. 

29.  The  following  is  a  method  of  turning  a  piece  of  work  from  end 
to  end  without  resetting  the  tool.     Turn  up  to  about  one-half  the  length 
of  the  work,  stop  the  feed,  then  stop  the  lathe,  now  take  the  work  out 
of  the  lathe  and  run  the  carriage  back  to  the  dead  centre,  then  reverse 
the  work,  and  turn  off  the  remainder.     If  the  cross-feed  screw  has  not 
been  moved,  or  the  tool  badly  worn,  both  ends  of  the  work  will  be  of 
the  same  diameter. 


16  MACHINE  SHOP  NOTES. 

30.  Speed  for  Turning.  — Card  101-A.  — For  the  roughing  cut,  use 
the  second  speed,  and  the  third  speed  for  the  finishing  cut,  "  back  gears 
out." 

Feed  for  Turning.  —  Card  101-A.  —  Use  the  second  feed  for  the 
roughing  cut,  and  the  finest  feed  for  the  finishing  cut.  For  gear  feed, 
use  a  gear  with  49  teeth  on  the  feed  spindle,  and  98  on  the  lead  screw. 

TAPEE  TTTENING-  AND  FITTING.— CAED  101-B. 

31.  if  the  taper  is  given  as  so  much  per  foot,  the  distance  to  set 
the  tailstock  over  can  be  readily  calculated.     For  example,  if  the  tail- 
stock  is  set  £"  out  of  liue,  the  lathe  will  turn  a  taper  of  one  inch  to 
the  distance  between  the  centres,  whether  that  be  more  or  less. 

If,  for  instance,  the  distance  between  the  centres  is  one  foot,  the 
taper  will  be  one  inch  to  the  foot;  if  the  distance  is  two  feet,  the 
taper  will  be  one-half  inch  to  the  foot,  etc. 

32.  Lathe  with  Taper  Attachment.  —  It  is  comparatively  simple  to 
turn  a  taper  with  a  lathe  that  has  a  taper  attachment,  which  may  be 
described  briefly  as  follows :  Three  brackets  are  bolted  to  the  back  of 
the  lathe  bed,  on  the  centre  one  of  which  is  pivoted  a  bar  supplied  with 
a  dove-tail  groove  along  its  entire  length ;  this  bar  is  also  supplied  at 
its  ends  with  circular  T  slots  in  which  bolts  carried  by  the  two  other 
brackets  work,  which  bolts,  on  being  tightened,  serve  to  hold  the  bar 
firmly  in  place.     One  of  the  end  brackets  is  graduated  so  that  the  bar 
can   be   set  to  turn  tapers  given  in  inches  per   foot.     A  nicely  fitted 
block,  working  in  the  groove  of  the  bar,  is  attached  to  the  cross  slide 
of  the  slide  rest,  and  thus  the  tool  is  made  to  move  in  obedience  to  the 
slot  in  the  bar  instead  of  the  ways  of  the  lathe,  giving  the   desired 
taper. 

33.  Second   Method  of    Taper  Turning. — The  method  to  be  used 
with  Card  101-B  is  as  follows :  Get  a  cutting-off  tool ;  set  its  shank  at 
right  angles  to  the  work,  and  its  point  the  same  height  as  the  point  of 
the  lathe  centres ;  also  be  sure  that  ths  tool  will  clear  itself  and  not  ride 
on  the  work.     Lay  off  on  the  work   the  length  of  the  taper  desired, 
with  the  cutting-off  tool  cut  a  groove  at  both  ends  of  the  required  taper, 
leaving  the  diameter  of  the  work  at  the  bottom  of  each  groove  just  -fa" 
larger  than  the  finished  size  of  the  taper  at  that  point. 

Get  a  taper-setting  gauge  and  set  the  holder  in  the  tool  post  at 
right  angles  to  the  work.  Place  the  point  of  the  feeler  alternately  iu 
each  groove,  and  adjust  the  tailstock  (or  taper  attachment)  until  it  will 
touch  the  bottom  of  both  grooves  the  same ;  the  lathe  will  then  be  set 
to  turn  the  desired  taper,  as  near  as  is  practicable  without  resort  to  try- 
ing the  work  in  the  taper  hole. 

Use  the  same  tool  in  the  same  manner  as  in  straight  turning,  with 


STRAIGHT   FITTING.  17 

this  exception,  that  to  turn  a  perfect  taper  it  is  absolutely  necessary  to 
have  the  point  of  the  tool  at  the  same  height  as  the  points  of  the  lathe 
centres.  It  will  be  found  necessary  to  try  the  taper  in  the  hole  after 
the  first  or  second  cut,  in  order  to  exactly  adjust  the  tailstock. 

To  try  a  taper  in  a  sleeve,  or  in  its  place,  make  a  light  chalk  mark 
along  it  from  end  to  end,  smoothing  the  chalk  with  the  finger ;  press  it 
into  the  hole,  and  partially  rotate  it ;  also  attempt  to  vibrate  the  taper 
in  the  sleeve,  observing  at  which  end  there  is  the  most  lateral  movement : 
such  movement  will  indicate  how  the  taper  fits.  If  the  fit  is  correct, 
the  appearance  of  the  chalked  line  will  indicate  it,  and  there  will  be  no 
lateral  movement.  Having  fitted  the  taper  as  nearly  as  possible  with 
a  lathe  tool,  turn  it  down  to  the  required  diameter,  calipering  it  at  the 
small  end  :  the  final  cut  should  be  light,  not  heavier  than  -fa".  To  finish 
the  taper,  chalk  a  line  along  it  (if  it  has  to  be  fitted  with  great  accuracy, 
cover  the  inside  of  the  hole  with  a  light  coat  of  prussian  blue) ,  try  it 
in  the  hole,  noting  where  it  bears ;  then  run  it  at  a  high  speed,  and 
with  an  8"  "  mill  bastard  "  file,  ease  off  the  parts  that  bear  the  hardest, 
continuing  until  it  fits  accurately. 

The  file  strokes  should  be  made  under  a  light  pressure,  and  after 
every  few  strokes  the  cuttings  should  be  cleared  from  the  file  with  a 
file  card. 

As  filing  tends  to  destroy  the  cylindrical  truth  of  the  work,  the  file 
should  only  be  applied  to  erase  the  tool  marks. 

Speed  for  Taper. — Card  101-B.  —  For  the  roughing  cuts,  use  the 
second  speed,  and  the  third  speed  for  the  finishing  cut,  "  back  gears 
out." 

Feed  for  Taper.  —  Card  101-B. — For  the  roughing  cuts,  use  the 
second  feed,  and  the  finest  feed  for  the  finishing  cut.  For  gear  feed, 
use  a  gear  with  49  teeth  on  the  feed  spindle,  and  98  on  the  lead  screw. 

STRAIGHT  FITTING. -CARD  101-B. 

34.  In  a  fit  of  any  kind,  care  should  be  taken  to  turn  the  work  so 
near  the  diameter  of    the  hole  that  it  will  only  be  necessary  to  file 
out  the  tool  marks,  in  order  to  make  it  fit  as  desired. 

This  piece  is  to  fit  a  1"  cylindrical  gauge.  The  finishing  cut  should 
be  very  light,  and  should  leave  the  piece  so  that  it  will  just  enter  the 
hole  tightly  ;  then  running  it  at  the  highest  speed,  erase  the  tool  marks 
with  an  8"  "mill  bastard"  file,  trying  it  in  the  hole  occasionally  to 
ascertain  if  the  fit  is  maintained.  This  should  be  a  close  fit. 

Use  the  same  speed  and  feed  as  on  straight  turning,  Card  101-A. 

BOLT  TURNING.  —  CAED  104, 

35.  The  bolt  being  wrought  iron,  use  lard  oil  in  drilling  and  counter- 
sinking ;  the  countersinks  when  finished  should  be  about  1"  in  diameter. 


18  MACHINE  SHOP  NOTES. 

The  turning  tools  must  be  very  keen  edged,  should  have  a  top  rake  of 
about  35°,  and  the  diamond  point  very  slightly  rounded. 

Feed.  —  For  the  roughing  cut,  use  the  second  feed,  and  the  finest  feed 
for  the  finishing  cut. 

Speed.  —  For  both  squaring  and  turning,  use  the  third  speed,  with  the 
"back  gears  out." 

Squaring.  —  "Square  up"  the  outside  of  the  head  first;  then  the 
opposite  end  of  the  bolt  to  within  -^"  of  the  required  length.  Now 
recountersink,  if  necessary,  and  take  the  finishing  cuts,  first  on  the  out- 
side of  the  head;  then  put  a  "clamp  dog"  on  the  head,  and  take  the 
finishing  cut  on  the  opposite  end  to  the  exact  length. 

Turning.  —  Set  the  "diamond  point"  tool  around  to  the  left  far 
enough  so  that  you  can  "turn  up"  to  within  ^"  of  the  head,  without 
having  the  dog  strike  the  carriage,  or  having  to  reset  the  tool.  With 
the  first  cut  turn  the  bolt  to  within  •£%"  of  the  required  diameter  ;  then 
"dog  on"  to  the  small  end,  and,  with  a  left-hand  side  tool,  "square 
up"  the  inside  of  the  head  to  within  ^¥"  of  the  required  thickness.  As 
this  bolt  must  fit  a  ^"  cylindrical  gauge,  the  finishing  cut  should  leave  it 
so  that  the  end  will  enter  the  hole  tightly.  "  Square  up  "  the  head  from 
the  inside  to  the  required  thickness. 

Filing.  —  Run  at  the  highest  speed,  and  erase  the  tool  marks  with  an 
8"  "  mill  bastard  "  file,  trying  the  bolt  in  the  hole  occasionally  to  ascertain 
if  the  fit  is  maintained.  It  should  be  an  easy  fit,  neither  tight  nor  loose. 

36.  Preparation  for  cutting  the  Thread.  —  Reduce  the  part  of  the 
bolt  that  is  to  be  threaded  ^"  in  diameter.  Drill  and  tap  a  nut ;  then 
screw  it  upon  a  nut  ai'bor,  and  "  square  it  up  "  to  the  exact  thickness. 

If  all  the  foregoing  operations  have  been  carefully  performed,  you  are 
now  ready  to  cut  the  thread. 

Tapping.  —  The  diameter  of  a  hole  that  is  to  be  tapped  with  a 
V-thread  tap  should  equal  the  diameter  of  the  tap  at  the  root  of  the 
thread,  except  on  cast  iron ;  then  the  hole  should  be  large  enough  to 
permit  only  of  three-quarters  of  a  full  thread. 

Oil  in  Tapping.  —  Always  freely  supply  a  tap  witli  lard  oil  when 
used  upon  wrought  iron,  steel,  cast  iron,  brass,  and  composition ;  but  in 
tapping  lead,  or  any  soft  metal,  oil  is  not  necessary. 

Milling  Head  and  Nut.  —  The  bolt  head  and  nut  may  be  *'  milled  " 
either  before  or  after  the  thread  is  cut. 

Chamfering.  — After  the  bolt  head  and  nut  are  "  milled  "  they  must 
be  chamfered.  To  do  this,  set  the  side  tool  at  an  angle  of  about  45°, 
and  chamfer  the  outside  corner  of  the  nut  and  bolt  until  there  is  about 
•gV'  flat  on  the  corner  of  the  short  diameter. 

Filing  and  Finishing.  —  After  the  head  and  nut  are  chamfered,  the 
sides  should  be  filed  with  an  8"  "  hand-smooth  "  file,  and  finished  with 
No.  90  emery  cloth. 


SCREW  CUTTING. 


19 


SCREW  CUTTING. 

37.  Lathe  Dog.  —  Fasten  the  dog  on  the  work  firmly,  for  it  must 
not  slip.  If  the  face  plate  of  the  lathe  has  more  than  one  slot  in  it, 
put  a  chalk  mark  near  the  slot  into  which  you  put  the  tail  of  the  udog." 
Whenever  the  work  is  taken  out  of  the  lathe,  it  must  be  put  back  with 
the  tail  of  the  "  dog  "  in  that  slot. 

Threaded  Part.  — On  bolts,  etc.,  turn  the  part  which  is  to  be  threaded 
-fa'1  under  size. 

Recess.  — If  at  the  commencement  or  the  termination  of  a  thread  it 
be  necessary  to  cut  a  recess,  use  a  round-nosed  tool  for  that  purpose. 


Fig.  3. 


Fig.  4. 


38.  Centre  Gauge. — In  Fig.  3,  A  represents  a  centre  gauge  and 
gauge    for   grinding   and  setting  a  V-thread   tool ;    the  angles  of  this 
gauge  are  60°.    Care  should  be  taken  to  grind  the  tool  to  fit  the  gauge  ; 
the  tool  should  be  given  top  rake  enough  to  make  it  cut  clean,  and  only 
enough  bottom  rake  to  clear  well  and  not  rub  against  the  thread. 

How  to  Set  a  V-Thread  Tool.  — Fig.  3  represents  a  piece  of  work  held 
between  the  centres  of  a  lathe.  Applying  the  gauge  as  shown  in  the 
figure,  the  V  tool  can  be  set  at  right  angles  to  the  work  and  then  fastened 
in  place. 

Height  of  Tool.  —  Set  the  point  of  the  tool  at  the  same  height  as 
the  points  of  the  lathe  centres. 

39.  Stop  Gauge.  —  With  the  cross-feed  screw  run  the  tool  in  until 
the  point  touches  the  work,  then  put  on  and  adjust  the  stop  which  regu- 
lates the  depth  of  the  cut. 

40.  Pitch.  —  The  pitch  of  a  thread  is  the  distance  between  the  cen- 
tres of  two  threads. 

Threads  per  inch  signifies  the  number  of  threads  contained  in  one 
inch,  measuring  at  the  root  of  a  V  thread  and.  at  the  right  edge  of  a 
square  thread. 

41.  Index.  —  With  each  lathe  there  is  a  screw-cutting  index,  giving 
the  number  of  "  threads  per  inch"  that  can  be  cut  on  the  lathe,  and 
the  change  gears  used  in  cutting  the  same. 


20  MACHINE   SHOP   NOTES. 

The  first  column  of  figures  represents  the  number  of  threads  per 
inch ;  the  second  column,  the  number  of  teeth  on  the  gear  used  on  the 
"  feed  spindle  "  ;  the  third  column,  the  number  of  teeth  on  the  gear  used 
on  the  lead  screw. 

On  any  of  the  shop  lathes  you  will  have  to  consider  only  the  gear 
on  the  lead  screw  and  the  gear  on  the  feed  spindle  ;  the  intermediate 
gear  can  be  of  any  size  that  will  connect  them. 

For  example  :  if  it  is  desired  to  cut  a  screw  of  "  thirteen  pitch"  (thir- 
teen threads  to  one  inch) ,  find  thirteen  in  the  first  column  ;  the  numbers 
opposite  in  the  second  and  third  columns  are  96  and  78  respectively. 
Place  a  gear  with  96  teeth  on  the  feed  spindle,  and  a  gear  with  78 
teeth  on  the  lead  screw,  and  adjust  the  intermediate  gear  to  the 
same. 

42.  Putnam  Lathe.  —  When  using  a  "Putnam"  lathe,  always  dis- 
connect the  carriage  by  dropping  the  pinion  that  runs  in  the  rack,  which 
can  be  done  by  loosening  a  nut  that  is  placed  on  the  outside  of  the 
apron ;    then  connect  the  carriage  to  the  lead  screw  by  means  of  the 
"  clamp  nut"  attached  to  the  back  of  the  carriage. 

43.  The  Brown  &  Sharpe  and  Pratt  &  Wiritaey  lathes  have  the 
lead   screw   and   feed   shaft   combined   in  one.      In   this   case   simply 
throw  in  the  "clamp  nut"  by  turning  the  small  crank  handle  that  is 
located  on  the  lower  part  of  the  apron,  right-handed.     Be  sure  with 
these  lathes  that  the  traverse  feed  is  out. 

Speed.  —  On  work  one  inch  and  less  in  diameter  use  the  first  speed 
"  out  of  gear,"  at  least  as  slow  as  that  until  you  can  manage  the  lathe 
properly. 

Oil.  — Use  lard  oil  on  steel  and  wrought  iron,  but  not  on  cast  iron. 

44.  To  cut  a  right-hand  screw,  begin  at  the  right-hand  end  of  the 
work  and  cut  towards  the  left.     The  first  time  over  just  allow  the  point 
of  the  tool  to  touch  the  work  sufficiently  to  "  line  out"  the  thread ;  then 
lay  a  scale  on  the  work  and  count  the  threads  per  inch  to  see  if  the 
pitch  is  right 

With  one  hand  on  the  handle  of  the  cross-feed  screw  run  the  tool 
back  far  enough  to  clear  the  work ;  with  the  other  hand  reverse  the 
lathe  until  the  tool  is  traversed  to  the  end  of  the  work  ;  then  feed  in 
and  take  another  cut.  The  cuts  at  first  can  be  quite  heavy,  but  as  the 
thread  approaches  its  finished  size  they  should  be  very  light.  The 
depths  of  the  cuts  are  regulated  by  means  of  the  stop  screw,  which  is 
adjusted  while  running  the  carriage  back. 

Fitting  the  Thread  to  the  Nut.  —  When  the  top  of  the  thread  gets 
nearly  sharp,  take  the  work  out  of  the  lathe  and  try  the  nut  on  it  to 
ascertain  if  it  fits  ;  if  it  does  not,  take  another  cut  and  try  again,  con- 
tinuing until  the  thread  will  fit  the  nut.  This  applies  to  a  sharp  V 
thread  only. 


CHUCKING.  21 

45.  Left-Hand  Thread.  —  lu  cutting  a  left-hand  thread,   gear  the 
same  as  in  cutting  a  right-hand  thread,  with  the  exception  that  the  feed 
motion  has  to  be  reversed.     On  a  "Putnam"  lathe   this   is  done  by 
means  of  two  intermediate  gears  ;  on  a  "Brown  &  Sharpe"  or  a  "Pratt 
&  Whitney  "  lathe,  it  is  done  by  means  of  a  lever  on  the  headstock. 

To  cut  a  left-hand  screw,  begin  at  the  left  and  cut  to  the  right.  At 
the  beginning  of  the  thread  it  will  be  best  to  cut  a  recess  as  deep  as  the 
thread  to  start  the  tool  from.  With  these  few  exceptions,  the  operation 
is  the  same  as  in  right-hand  thread  cutting. 

46.  Inside  Thread. — Most  of  the  operations  in  inside  thread  cutting, 
such  as  "gearing  up"  the  lathe,  adjusting  the  height  of  the  tool,  etc., 
are  similar  to  outside  thread  cutting. 

If  the  work  is  cast  iron,  the  hole  should  be  bored  or  drilled  large 
enough  to  allow  only  three-quarters  of  a  full  thread ;  that  is  all  that  is 
necessary  on  a  V  thread  with  cast  iron,  unless  the  thread  has  to  be  steam 
tight. 

The  Manner  of  setting  the  Tool  is  shown  in  Fig.  4  (p.  19).  The  work 
is  supposed  to  be  held  in  a  chuck,  the  hole  either  drilled  or  bored  to  the 
required  diameter,  and  the  end  "  squared  up."  By  applying  the  gauge 
as  shown,  the  tool  can  be  set  at  right  angles  to  the  work  axis. 

Stop  Gauge.  —  To  regulate  the  depth  of  each  cut,  the  collar  on  the 
stop  sci'ew  must  be  on  the  inside  of  the  clamp,  and  the  screw  must  be 
turned  in  the  direction  opposite  to  that  used  in  outside  thread  cutting. 

Oil. — Use  lard  oil  on  steel  and  wrought  iron,  but  not  on  cast  iron, 
except  it  be  necessary  to  run  a  tap  through  the  hole  to  size  it,  when  oil 
may  be  used. 

.       CHUCKING. 

47.  Chucks  are  devices  for  holding  work  or  tools,  and  are  made  of 
various  sizes. 

Independent  Chucks  are  those  in  which  each  jaw  is  moved  separately. 

Universal  Chucks  are  those  in  which  the  jaws  move  simultaneously  to 
grip  or  release  the  work. 

Combination  Chucks  are  those  in  which  the  jaws  may  be  moved  inde- 
pendently or  simultaneously. 

Small  universal  (or  drill)  chucks,  although  mainly  used  to  drive 
drills,  may  also  be  used  to  drive  very  small  work  that  is  to  be  chucked 
or  turned. 

When  asking  for  a  chuck  at  the  tool  room,  be  sure  and  give  the 
swing  and  make  of  the  lathe  you  desire  to  use  it  on.  (The  swing  of  a 
lathe  is  twice  the  distance  from  the  centre  to  the  nearest  point  on  the  bed.) 

48.  To  put  the  Chuck  on  the  Spindle,  remove  the  live  centre  and 
plug  the  hole  with  clean  waste ;  then  take  off  the  face  plate  by  turning 


22  MACHINE   SHOP  NOTES. 

its  top  towards  the  front  of  the  lathe ;  start  it  off  by  means  of  a  tangen- 
tial blow  of  either  a  lead  hammer  or  a  block  of  wood.  See  that  the 
thread  in  the  chuck  and  on  the  spindle  is  free  from  chips  and  grit ;  put 
a  little  oil  on  the  spindle  thread  ;  then  hold  the  chuck  in  the  right  hand, 
and  with  the  left  rotate  the  spindle  slowly  by  means  of  the  belt  until  the 
chuck  comes  to  the  shoulder  on  the  spindle.  Do  not  force  a  chuck  or  a 
face  plate  on  to  the  spindle  of  a  lathe,  as  each  should  go  on  freely ;  if 
they  do  not,  there  must  be  a  cause  ;  it  may  be  chips  in  the  thread.  In 
any  case,  the  cause  should  be  found  and  removed. 

Direction  of  Chucking. — "Work  that  has  to  fit  a  shaft  of  any  kind 
should  be  chucked  in  the  same  way  that  it  has  to  go  on  the  shaft. 

Pulleys.  —  If  it  be  possible,  when  chucking  a  pulley,  place  each  spoke 
opposite  a  jaw  to  receive  the  strain.  The  jaws  must  be  "  set  up  "  tight 
enough  to  keep  the  work  from  shifting. 

49.  "Truing  up"  Work  in  an  Independent  Chuck  is  accomplished 
by  placing  the  work  in  the  chuck  and  setting  the  jaws  against  it  tightly 
enough  to  keep  it  in  position ;  run  the  lathe  at  a  high  speed ;  with  the 
hand  resting  on  the  carriage,  hold  a  piece  of  chalk  so  that  it  will  just 
touch  the  work,  then  stop  the  lathe,  and  if  the  chalk  has  touched  all 
around  the  work,  it  is  "  true"  ;  but  if  the  chalk  has  only  touched  a  part, 
loosen  the  jaw,  or  jaws,  opposite  that  part,  and  set  the  others  in  ;  rub 
the  chalk  mark  out  and  try  again,  continuing  until  the  work  runs  true. 

Card  105.  —  To  get  good  results,  the  pulley  (Card  105)  should  be 
"  trued  up  "  from  the  inside  of  the  rim. 

50.  "  Truing  up  "  Work  in  a  Universal  Chuck.  —  Place  the  work  in 
the  chuck,  "set  up"  the  jaws  by  means  of  one  screw,  then  run   the 
lathe  at  a  high  speed,  and  use  chalk  as  before  ;  if  it  does  not  run  true 
enough,  loosen  the  jaws  and  turn  the  work  about  one-quarter  of  a  revo- 
lution, then  "  set  the  jaws  up,"  and  try  it  again  ;  when  right,  tighten  all 
the  screws. 

51.  The  Tools  used  in  chucking  are  the  drill  rest,  the  chucking  drill, 
and  the  chucking  or  flat  reamer.     Hand  reamers  are  of  standard  diame- 
ter, and  are  used  by  hand,  with  the  work  held  in  a  vise.     Chucking 
reamers  should  be  from  three  to  five  thousandths  inches  smaller  than 
the  hand  reamer,  and  the  drill  should  be  at  least  -fa"  smaller  than  the 
chucking  reamer. 

52.  Manner  of  setting  a  Drill  Rest.  — Fasten  the  drill  rest  in  the 
tool  post,  as  shown  (plan  view)  in  Fig.  5. 

The  centre  of  the  slot  should  be  at  the  same  height  as  the  lathe  centres. 
To  insure  this,  run  the  dead  centre  into  the  slot,  and  adjust  the  drill 
rest  by  means  of  the  elevating  and  cross-feed  screws,  until  the  centre 
just  touches  the  top  and  bottom  edges  simultaneously,  and  is  in  the 


CHUCKING.  23 

centre  of  the  slot  lengthwise  (approximately)  ;  then  traverse  the  carriage 
until  the  drill  rest  is  within  -J-"  of  the  work. 


Fig.  0. 

Oil  should  be  used  on  steel  and  wrought  iron,  but  not  on  cast  iron. 
Speed.  — For  a  1"  drill,  run  on  the  second  speed,  and  for  a  £"  drill, 
on  the  third  speed. 

53.  Starting  the  Drill. — Place  the  drill  in  the  slot,  with  its  point 
against  the  centre  of  the  work  (as  near  as  the  eye  can  locate) ,  and  the 
other  end  on  the  dead  centre.     Start  up  the  lathe,  hold  the  drill  firmly 
in  the  slot  with  a  monkey-wrench,  and  feed  in  until  it  cuts  to  about 
half  the  depth  of   its  point ;    then   loosen  your  hold  on  the  monkey- 
wrench,  and  feed  in  quite  rapidly.      If  the  drill  moves  sidewise,  the 
hole  is  not  true ;  this  being  the  case,  again  hold  the  drill  firmly  with 
the  monkey-wrench,  and  feed  in  slowly  until  the  side  of  the  hole  that 
runs  out  is  cut  away  ;  then  loosen  your  hold  on  the  monkey- wrench, 
and  feed  in  as  before.     If  the  drill  does  not  move  sidewise,  it  is  central, 
and  the  hole  is  true.     This  "truing  up"  must  be  done  before  the  drill 
cuts  to  its  full  diameter. 

When  the  Drill  begins  to  break  through,  hold  it  on  the  dead  centre  ; 
when  through,  stop  the  lathe  and  take  out  the  drill ;  next  put  a 
chucking  reamer  through,  using  a  monkey-wrench  to  steady  it  while 
starting. 

54.  How  to  use  a  Hand  Reamer. — Hold  the  work  in  a  vise,  and 
ream  through  the  same  way  that  it  has  to  fit  on  the  shaft.     Use  oil  on 
steel  and  wrought  iron,  but  not  on  cast  iron,  except  a  little  on  the  shank 
of  the  reamer.     Always  turn  a  reamer  forward  and  bear  down  on  it 
lightl}',  but  never  under  any  condition  turn  it  backward.     Hand  reamers 
should  be  used  very  carefully. 

AEBOKS. 

55.  An  arbor  or  mandrel  is  a  cylindrical  piece  which  is  forced  or 
driven   into   hollow  work   in   order   to  furnish  centres  upon  which  to 
revolve  it.     For  example :    a  pulley  having  been  chucked  and  hand- 


24  MACHINE   SHOP   NOTES. 

reamed  requires  an  arbor  to  be  driven  into  it  in  order  to  supply  centres 
to  hold  it  while  it  is  turned  in  the  lathe.  Arbors  are  usually  made  of 
cast  steel,  especially  when  small. 

56.  How  to  use  an  Arbor.  —  Rub  a  little  oil  on  the  arbor,  put  the 
small  end  in  the  hole  the  same  way  that  it  was  reamed ;  then,  with  a 
copper  hammer,  drive  in  the  arbor  tight  enough  to  prevent  the  work 
from  slipping. 

57.  How  to  make  a  £"  Arbor.  —  (1)  A  good  quality  of  cast  steel 
should  be  used  in  making  this  arbor.     (2)  It  should  be  annealed,  then 
carefully,  centred  and  "  squared  up"  to  the  required  length  with  a  side 
tool.     (3)   A  portion  of  the  ends  should  be   turned  to  within  ^T"  of 
finished  size,  using  a  diamond-point  tool.      (4)  A  small  recess  should 
be  formed  with  a  side  tool,  about  the  countersinks  (as  shown  on  card), 
to  prevent  the  edges  of  the  countersink  from  being  injured  when  the 
end  of  the  ai'bor  is  struck.     (5)   See  that  the  countersinks  are  of  the 
given  diameter.     (6)  Turn  the  reduced  portion  to  the  required  diameter 
and  file  sufficiently  to  erase  the  tool  marks,  running  the  lathe  at  a  high 
speed  and  using  an  8"  "  mill  bastard  "  file  ;  also  slightly  round  the  corner 
of  the  ends  with  a  "graver."     (7)  Polish  the  reduced  portion  and  the 
ends,   except  the  countersinks,  using  a  speed  lathe.      (8)  File  a  flat 
place  on  the  reduced  portion  of  the  ends  (as  shown  on  card)   to  receive 
the  set  screw  of  the  lathe  dog ;  use  an  8"  "hand  smooth  "  file  and  finish 
with  emery  cloth.      (9)   Turn  the  main  body  of  the  arbor  to  within  -^" 
cf  finished  size  ;  file  a  flat  place  on  the  end   (as  shown  on  card)  and 
stamp  the  diameter  of  the  arbor  there,  using  a  V  block  to  hold  the 
arbor  and  y1^"  figures  for  stamping.     Not  until  all  the  foregoing  opera- 
tions have  been  performed  is  the  arbor  ready  to  be  hardened.     Use  oil 
in  drilling  and  countersinking. 

Speed  and  Top  Rake.  —  Remember  that  the  stock  is  cast  steel,  and 
the  cutting  speed  should  be  less  than  on  the  same  diameter  of  machinery 
steel,  and  that  the  diamond  point  and  side  tool  should  have  a  top 
rake  of  about  20°. 

Round  Corners. — In  turning  off  the  reduced  portion  do  not  leave 
a  square  corner,  which  would  be  very  liable  to  cause  cracking  in  hard- 
ening. 

The  ^j"  left  on  the  main  part  is  to  be  ground  off  after  hardening. 

OTLINDEICAL   GEINDING, 

58.  Grinding  machines  are  employed  to  finish  work  more  smoothly 
and  much  more  accurately  than  can  be  done  with  steel  cutting  tools. 
They  are  very  useful,  as  the}7  can  be  made  to  operate  on  hardened  as 
well  as  soft  work  and  produce  the  same  degree  of  accuracy. 


CYLINDRICAL   GRINDING.  25 

Cylindrical  and  surface-grinding  machines  are  not  designed  to  re- 
move a  large  amount  of  stock,  but  simply  to  reduce  the  work  surface  to 
true  and  exact  dimensions. 

They  operate  on  essentially  the  same  principle  as  the  engine  lathe, 
the  steel  cutting  tools  of  the  engine  lathe  being  replaced  by  a  rapidly 
revolving  emery  wheel,  driven  by  an  independent  drum  or  wide  pulley. 
Therefore,  if  the  engine  lathe  is  well  understood,  there  will  be  no  diffi- 
culty in  understanding  the  grinding  machine  after  a  brief  examination. 

Motion  of  Work.  —  In  all  cases  the  motion  of  the  work  must  be  in 
a  direction  opposite  to  the  wheel  at  the  cutting  point. 

The  Speed  of  the  Work  can  be  regulated  as  on  an  engine  lathe,  high 
speed  being  used  for  small,  and  slow  speed  for  large,  diameters. 

The  Speed  of  the  Emery  Wheel  should  be  about  5000  feet  per  minute. 

59.  Emery  Wheels.  —  No  definite  rule  can  be  given  by  which  emery 
wheels  may  be  selected  for  different  kinds  of  work ;  much  depends  on 
the  nature  of  the  work.  No.  60  emery  will  give  as  good  results  on 
hardened  work  as  No.  90  will  on  soft  work.  When  a  large  amount  of 
stock  has  to  be  ground  off,  it  is  best  to  use  about  No.  40  for  roughing 
and  No.  120  for  finishing.  Where  one  wheel  is  used  for  both  roughing 
and  finishing,  and  there  is  only  a  small  amount  of  stock  to  be  ground 
off,  it  will  be  profitable  to  use  about  No.  100  emery. 

The  degree  of  coarseness  of  emery  wheels  is  denoted  by  the  "  num- 
ber" of  the  emery  used  in  their  composition.  See  §  65. 

60.  Care  of  Grinding  Machines.  —  The  wearing  surfaces  should  be 
well  oiled  and  all  parts  kept  as  clean  as  possible  ;  for  if  emery  gets  into 
the  bearings,  the  machine  soon  becomes  unreliable  and  short-lived  for 
accurate  work.     Any  emery  grinder  requires  great  care  to  keep  it  clean. 

True  Centre  Holes  and  Centres  are  absolutely  necessary  to  obtain  good 
results  when  the  grinding  is  done  on  centres. 

Relieve  the  Dead  Centre.  —  In  grinding,  the  work  becomes  heated  and 
expands,  thus  binding  on  the  dead  centre  ;  therefore  be  sure  that  the 
work  is  kept  free,  by  frequently  relieving  and  oiling  the  dead  centre. 

61.  Arbor  Grinding.  —  The  following  method  is  adopted  in  grinding 
a  ^"  arbor.     The  arbor  is  supposed  to  be  marked,  hardened,  and  tem- 
pered, and  the  diameter^"  large.     Get  the  special  "  dog"  from  the  tool 
room  and  fasten  it  on  the  marked  end  of  the  arbor,  take  a  light  cut 
over  its  entire  length,  then  caliper  both  ends  with  a  micrometer  caliper 
(see  §  67)  ;  the  large  end  (which  is  the  marked  end)  should  be  about 
four  thousandths  larger  than  the  small  end  ;  if  it  does  not  caliper  as 
required,  adjust  the  machine  until  it  will  grind  the  proper  taper. 

Light  Cuts. — To  produce  a  true  surface,  it  is  necessary  to  take  a 
very  light  cut  as  the  work  approaches  its  finished  size,  which  is  five 


26  MACHINE   SHOP   NOTES. 

hundred  thousandths  of  an  inch  one  inch  from  the  small  end.  In  this 
case  the  arbor  should  fit  the  \"  hand-reamed  hole  in  the  pulley,  so  that 
the  pulley  will  drive  about  half  way  on  the  arbor. 

Cuts  may  be  taken  both  ways,  but  always  commence  at  the  small 
end  to  take  the  finishing  cut,  so  that  you  can  get  the  size  of  that  end. 

General  Suggestions.  —  It  must  be  remembered  that  to  get  good 
results  on  work  even  as  simple  as  an  arbor,  (1)  the  final  cut  must  be 
very  light ;  (2)  that  you  must  not  take  a  cut  over  its  entire  length  and 
then  caliper ;  but  take  a  cut  of  about  %"  in  length,  then  stop  the  ma- 
chine and  caliper,  or  try  it  in  the  pulley  ;  (3)  that  to  caliper  work  on 
centres,  the  caliper  is  put  over  the  work  and  adjusted  by  means  of  the 
knurled  head  until  the  friction  slips,  the  reading  being  then  taken  ; 
(4)  that  you  must  put  a  collar  under  the  hub  of  the  pulley  when  driving 
the  arbor  into  it,  in  order  to  prevent  breaking  the  arms. 


PULLEY  TUKNING. 

62.  Parts   Finished.  —  Every  part   of  the   pulley  drawing  that  is 
marked  /  must  be  finished ;  that  is,  turned,  filed  or  scraped,  aud  pol- 
ished. 

To  be  remembered.  —  (1)  That  this  pulley  is  quite  slender  ;  therefore, 
do  not  take  a  heavy  cut  or  a  coarse  feed.  (2)  That  all  parts  marked/ 
must  be  roughed  out  before  any  part  is  finished. 

Speed. — Use  the  third  speed,  "back  gears  in,"  for  both  roughing 
and  finishing  cuts  on  the  face  and  edges  of  the  rim.  For  both  roughing 
out  and  finishing  the  hub,  use  the  third  speed,  "  back  gears  out." 

Feed.  —  Use  fine  feed  on  both  roughing  and  finishing  cuts. 

Tools.  —  To  turn  off  the  face,  both  roughing  out  and  taper,  a  dia- 
mond-point tool  is  employed  with  a  top  rake  of  about  20°  and  the 
point  slightly  rounded. 

To  turn  off  the  hub,  a  round-nosed  tool  is  employed  for  both 
roughing  and  finishing  cut. 

To  "square  up"  the  rim  and  the  end  of  the  hub,  a  round-nosed 
tool  is  employed  for  the  roughing  cut  and  a  facing  tool  for  the 
finishing  cut. 

63.  Order  of  Operations.  —  (1)  Turn  off  the  face  of  the  pulley  to  the 
given  diameter,  4£",  which  may  require  more  than  one  cut.     (2)  Turn 
off  the  hub  to  within  ^¥"  of  the  required  diameter.     (3)  "  Square  up" 
the  rim  and  the  ends  of  the  hub  to  within  fa"  of  the  required  size,  by 
clamping  the  carriage  aud  feeding  the  tool  from  circumference  to  centre. 
(4)  Take  the  finishing  cut  on  the  rim  and  the  sides  of  the  hub,  by 
clamping  the  carriage  and  feeding  the  tool  from  centre  to  circumference. 


POLISHING.  27 

(5)  Take  the  finishing  cut  on  the  hub.  (6)  The  taper  on  the  rim  is  J" 
in  5"  ;  the  arbor  being  5"  in  length,  set  the  dead  centre  out  of  line  £" 
toward  the  back  of  the  lathe.  Rub  chalk  on  the  face  of  the  pulley,  and 
with  a  pair  of  dividers  draw  a  line  midway  between  its  edges  ;  set  the 
diamond-point  tool  so  that  it  will  just  touch  at  this  line  and  feed  the 
tool  toward  the  headstock.  It  is  obvious,  that  to  taper  the  second  half, 
the  simplest  way  is  to  reverse  the  pulley  in  the  lathe  and  emplo}7  the 
tool  as  on  the  first  half.  (7)  Run  the  lathe  at  the  second  speed,  "  back 
gears  out,"  and  with  an  8"  "  mill  bastard  "  file  erase  the  tool  marks  on 
the  face  of  the  pulley.  (8)  Set  the  side  tool  at  an  angle  of  about  45°,  run 
the  lathe  at  a  slow  speed,  and  make  a  small  chamfer  on  the  inside 
corner  of  the  rim,  the  object  being  to  true  up  the  inside  edge  of  the  rim. 
(9)  Put  the  pulley  in  a  speed  lathe,  run  it  at  the  third  speed,  scrape  the 
hub  and  round  its  corner  by  means  of  the  "graver."  If  all  the  fore- 
going operations  have  been  carefully  performed,  the  pulley  is  now  ready 
to  be  polished. 

POLISHING. 

64.  The  Process  of  polishing  in  a  Lathe,  it  should  be  remembered, 
reduces  to  some  extent  the  size  of  the  work ;  the  amount,  though  small, 
is  yet  of  importance  where  exact  dimensions  are  necessary. 

Operations  Preparatory  to  polishing. — When  it  is  required  to  polish 
and  keep  the  work  as  true  and  parallel  as  possible,  it  should  be  finished 
very  carefully  with  lathe  tools,  file,  and  scraper ;  for  if  it  requires  much 
application  of  emery  to  obtain  the  necessary  polish,  the  surface  will  not 
be  smooth  and  true,  as  the  emery  cuts  out  the  most  where  the  metal  is 
most  porous. 

If  a  piece  of  work  is  to  be  polished,  the  finishing  cut  should  be  taken 
with  a  fine  feed,  and  at  as  quick  a  cutting  speed  as  the  hardness  of  the 
metal  will  permit.  With  fine  feed  and  quick  speed,  the  pores  of  the 
metal  do  not  show  ;  whereas  with  coarse  feed  the  pores  are  exposed  for 
quite  a  depth. 

Filing.  —  If  cylindrical,  the  surface  should  be  filed  enough  to  erase 
the  tool  marks,  using  a  "mill  bastard"  file  for  that  purpose. 

Scraping.  —  If  radial,  or  of  curved  outline,  the  surface  should  be 
scraped  with  a  well-oiled  stone  hand  scraper,  with  a  piece  of  leather  be- 
tween it  and  the  rest  to  prevent  the  scraper  from  chattering ;  the  scraper 
should  be  used  at  as  fast  a  speed  as  it  will  stand. 

65.  The  "Number"  of  Emery. — Emery  derives  its  graded  "num- 
ber" from  the  number  of  meshes  to  the  inch  in  the  silk  sieve  through 
which  it  is  sifted.     For  example,  emery  that  would  pass  through  a  sieve 
having  six  meshes  to  the  inch,  and  over  one  having  eight  meshes,  would 
be  called  No.  6  emery. 


28 


MACHINE   SHOP  NOTES. 


Grade  of  Emery  used  on  Different  Kinds  of  Work.  —  For  ordinary 
work  that  has  been  filed  or  scraped  very  carefully,  use  Nos.  60,  90,  120, 
and  flour-emery  cloth,  in  the  order  given,  with  lard  oil,  revolving  the 
work  at  a  very  fast  speed.  The  emery  cloth  should  be  wrapped  closely 
around  a  piece  of  wood.  To  afford  a  fulcrum  for  the  wood,  the  T  rest 
should  be  placed  a  short  distance  from  the  work. 

If  the  work  is  finished  very  carefully,  it  may  not  be  necessary  to  use 
No.  CO  emery  cloth ;  No.  90,  or  even  finer,  may  be  coarse  enough  to 
remove  the  file  or  scraper  marks. 

The  coarse  grade  should  be  used  until  all  the  file  or  scraper  marks  are 
removed,  each  successive  grade  being  emplo}-ed  until  it  has  entirely  re- 
moved the  marks  left  by  the  grade  previously  used.  The  emery  should 
be  moved  backwards  and  forwards  along  the  work  when  polishing  cylindri- 
cal surfaces,  so  that  the  marks  will  cross  and  recross  each  other. 

66.  The  Final  Polish  is  given  by  flour-emery  cloth,  moved  along  the 
work  very  slowly  and  under  a  light  pressure. 

On  a  Radial  Face,  the  emery  cloth  should  be  moved  continuously,  so 
that  it  will  approach  and  then  recede  from  the  centre  of  the  work,  the 
object  of  this  being  to  prevent  the  emer}1  from  cutting  rings  into  the 
surface. 

The  emery  cloth  should  be  changed  in  position  as  the  emery  wears 
off,  thus  bringing  all  parts  in  contact  with  the  work. 


MICROMETER  CALIPEE, 

67.   Directions  for  reading  a  Micrometer  Caliper.  —  The  work  to  be 
measured  is  introduced  between  the  points  of  the  screws  A  and  (7,  Fig.  6, 


1-8    .125 
1-4   .250 
3-8    .375 
1-2    .500 
5-8    £25 
3-4   .750 
7-8    .875 
16tHs. 
1     .0625 
3    .1875 
5    .3125 
7    .4375 
9 

11.6875    Providence.RJ.    37  "8437 

13  .8125  29    .9062 

15  .9375  31    .9687 


1  .0313 
3  .0937 
5  .1562 
7  .2187 
9  .2812 
11  .3437 
13  .4063 
15  .4687 
17  .5312 
19  .5937 
SI  .6562 


Fig.  6. 


the  distance  between  which  is  readily  adjusted  by  turning  the  thimble  D, 
which  is  connected  with  the  screw  (7.  The  screw  has  forty  (40)  threads 
per  inch  ;  therefore,  every  turn  of  it  will  open  the  caliper  twenty-five  thou- 


MICROMETER   CALIPER.  29 

sandths  of  an  inch  (.025").  The  number  of  turns  the  caliper  has  been 
opened  is  indicated  by  the  scale  on  the  hub  a,  which  is  graduated  forty 
(40)  divisions  to  the  inch,  and  the  fractional  part  of  a  turn  (or  its  equiv- 
alent in  thousandths)  is  indicated  by  the  scale  on  the  thimble  D,  which 
is  graduated  into  twenty-five  (25)  parts.  Hence,  to  read  the  caliper, 
count  the  number  of  whole  divisions  on  the  scale  of  the  hub  at  a,  and 
multiply  by  twenty-five  (25)  ;  then  add  the  number  of  divisions  counted 
on  the  scale  of  the  thimble  D.  The  result  will  be  the  distance  between 
the  screw  points  in  thousandths  of  an  inch. 

For  example :  as  set  in  the  figure  there  are  three  (3)  whole  divisions 
visible  on  the  scale  at  a,  which  gives  us  3  X  25  =  75.  Then  we  read 
five  (5)  divisions  on  the  thimble  D,  which,  added,  gives  us  3  x  25  +  5 
=  80,  eighty  thousandths  of  an  inch  (.080"). 

Note. — On  some  micrometer  calipers  the  screw  C  has  fifty  (50) 
threads  per  inch ;  hence  every  turn  of  it  will  open  the  caliper  twenty 
thousandths  of  an  inch  (.020"),  and  the  scale  of  the  thimble  D  is  grad- 
uated into  eighty  (80)  parts,  each  part  indicating  one  four-thousandth 
of  an  inch  or  twenty-five  hundred-thousandths  (.00025"). 

On  micrometer  calipers  not  having  a  frictional  connection  between  the 
screw  and  the  knurled  head,  care  should  be  taken  in  adjusting.  The 
hold  on  the  knurled  head  should  be  easy,  so  that  the  "feeling"  will 
indicate  when  contact  is  made.  This  feeling  being  the  same  each  time 
the  caliper  is  used,  the  readings  will  be  comparative. 


80  MACHINE  SHOP  NOTES. 

68.   Table  of  Common  Fractions  and  Decimal  Equivalents. 


A 

_ 

_ 

_ 

.015625 

I! 

_ 

_ 

_ 

.515625 

_ 

A 

— 

_ 

.03125 

— 

H 

— 

_ 

.53125 

A 

- 

- 

.046875 

ft 

- 

- 

.546875 

_ 

_ 

A 

_ 

.0625 

_ 

_ 

•fs 

_ 

.5625 

Tf 

- 

- 

.078125 

ft 

- 

- 

- 

.578125 

— 

A 

- 

— 

.09375 

— 

if 

— 

— 

.59375 

A 

- 

- 

.109375 

tt 

- 

- 

- 

.609375 

_ 

_ 

- 

i 

.125 

_ 

— 

— 

5 

.625 

A 

- 

- 

.140625 

ti 

- 

- 

- 

.640625 

— 

-fo 

— 

— 

.15625 

— 

ti 

— 

— 

.65625 

ii 

- 

- 

- 

.171875 

ft 

- 

- 

.671875 

_ 

_ 

TV 

_ 

.1875 

_ 

_ 

ii 

_ 

.6875 

ft 

- 

- 

.203125 

ft 

- 

- 

.703125 

— 

A 

— 

— 

.21875 

_ 

M 

— 

— 

.71875 

H 

- 

- 

.234375 

ft 

- 

- 

- 

.734375 

_ 

_ 

_ 

^ 

.250 

_ 

_ 

_ 

1 

.750 

H 

- 

- 

- 

.265625 

ft 

- 

- 

- 

.765625 

_ 

A 

— 

— 

.28125 

_ 

M 

_ 

_ 

.78125 

if 

- 

- 

.296875 

ft 

- 

- 

- 

.796875 

_ 

_ 

A 

— 

.3125 

_ 

_ 

if 

— 

.8125 

Ii 

- 

- 

.328125 

ft 

- 

- 

- 

.828125 

_ 

H 

_ 

_ 

.34375 

_ 

ft 

_ 

— 

.84375 

If 

- 

- 

.359375 

ft 

- 

- 

- 

.859375 

— 

— 

— 

1 

.375 

— 

_ 

— 

I 

.875 

If 

- 

- 

.390625 

fi 

- 

- 

.890625 

— 

if 

— 

— 

.40625 

_ 

II 

— 

— 

.90625 

Ii 

- 

- 

- 

.421875 

If 

- 

- 

- 

.921875 

— 

— 

A 

— 

.4375 

— 

_ 

if 

— 

.9375 

If 

- 

- 

.453125 

fi 

- 

- 

.953125 

— 

if 

— 

— 

.46875 

_ 

fi 

_ 

— 

.96875 

fi 

- 

- 

.484375 

ft 

- 

- 

- 

.984375 

— 

— 

— 

* 

.500 

— 

— 

— 

1 

1.000000 

SQUAKE-THEEAD  CUTTING.  -  OAED  116. 

69.    Square-Thread  Tool.  — For  cutting  square  threads  the  tool  shown 
in  Fig.  9  is  employed. 

Inclination  of  the  Tool.  —  The  sides  of  the  tool  AB  and  EF,  Fig.  7, 
should  be  inclined  to  the  body  of  the  tool,  the  degree  of  inclination 
depending  upon  the  pitch  of  the  thread  to  be  cut. 


SQUARE   THKEAD   CUTTING. 


31 


The  Method  of  finding  the  Degree  of  Inclination  is  shown  in  Fig.  8. 
Draw  the  lines  AD  and  AB  at  right  angles  to  each  other.  Make  the 
distance  AB  equal  to  the  root  circumference,  and  AC  equal  to  the 


Fig.  7. 


Fig.  10. 


pitch  of  the  thread  to  be  cut :  draw  BC ;  then  the  angle  BOD  will  be 
the  angle  which  the  root  of  the  thread  makes  with  the  axis  of  the  work, 
and  the  angles  of  the  sides  of  the  tool  should  differ  from  this  sufficiently 
to  give  the  necessary  clearance. 

The  tool  should  be  somewhat  narrower  at  D  and  B,  Fig.  9,  than  at 
C,  so  that  the  cutting  may  be  done  by  the  edge  C  entirely. 

Finishing  Tool.  —  The  width  of  a  finishing  tool  at  C  should  be  ex- 
actly one-half  the  pitch.  For  example,  if  the  thread  to  be  cut  is  six 
(6)  pitch,  the  width  of  the  tool  at  C  should  be  one-twelfth  of  an  inch 

/  i  "\ 
vrir  /• 

Roughing  Tool.  —  When  it  is  necessary  to  use  a  roughing  tool,  make 
the  width  at  C  about  one  hundredth  of  an  inch  (.01")  less  than  the 
finishing  tool. 

Coarse  Pitch.  —  For  a  very  coarse  pitch  the  tool  is  made  about  one- 
half  the  width  of  the  thread  groove,  and  a  groove  is  cut  on  the  work ; 
jthe  tool  is  then  moved  laterally  and  a  second  cut  is  taken.  The  right- 
and  left-hand  side  tools  are  then  employed  to  finish  the  sides  of  the 
thread. 

70.  Inside  Square-Thread  Cutting.  —  Fig.  10  represents  an  inside 
square-thread  tool.  The  inclination  is  found  by  the  same  method  as 
emplo3red  with  the  outside  tool.  As  this  tool  is  necessarily  rather 
slender,  the  cuts  should  be  light. 

Top  Bake  and  Oil.  —  Square-thread  tools,  when  employed  upon 
wrought  iron  and  steel,  should  have  some  top  rake,  and  be  freely 
supplied  with  lard  oil. 

Filing  up  Tools.  — Use  an  8"  "hand  smooth  "  and  a  "  dead  smooth" 
file  to  file  up  the  tools,  and  a  micrometer  caliper  to  measure  the 
width. 

Outside  Thread.  —  In  Fig.  11  the  manner  of  setting  a  square-thread 
tool  for  cutting  outside  threads  is  illustrated. 

Inside  Thread. — In  Fig.  12  the  manner  of  setting  an  inside  square- 
thread  tool  is  shown.  The  work  is  supposed  to  be  held  in  a  chuck,  the 
hole  bored  to  size,  and  the  end  "  squared  up." 


32 


MACHINE   SHOP   NOTES. 


71.    The  Nut.  —  The  stock  for  the  nut  is  held  in  the  jaws  of  a  chuck 
and  "  trued  up,"  and  a  ||"  hole  chucked  through  it;  then  a  boring  tool 


Fig.  11. 


Fig.  12. 


is  employed  to  bore  it  to  the  required  diameter,  which  should  be  about 
.01"  larger  than  the  diameter  of  the  tap  measured  at  the  root  of  the 
thread  ;  a  thread  is  now  cut  in  it,  with  an  inside  roughing  tool,  to  nearly 
the  diameter  of  the  tap ;  it  is.  then  held,  in  wooden  clamps,  in  a  vise, 
and  first  tap  No.  1,  and  then  tap  No.  2,  is  run  through  it.  (Oil  should 
be  used  freely  in  tapping.)  Now  it  should  be  screwed  on  a  nut  arbor, 
"squared  up"  to  the  required  length,  and  turned  to  the  given  diam- 
eter. A  facing  tool  is  used  in  taking  the  finishing  cut  on  the  ends. 

72.  Cutting  the  Thread  on  the  Shaft.  —  With  the  roughing  tool  take 
a  cut  on  the  shaft  to  the  required  length  of  thread  ;  then  remove  it  from 
the  lathe  and  drill  a  hole  at  the  termination  of  the  thread,  equal  in 
diameter  to  the  width  of  the  finishing  tool,  and  in  depth  to  the  depth  of 
the  thread.     The  lathe  should   be  stopped  when  the  tool  is  near  this 
hole  and  the  cut  continued  to  the  hole,  running  the  lathe  (by  pulling  the 
belt)  by  hand.     The  finishing  tool  should  be  set  so  that  it  will  cut  on 
both  sides  of  the  groove. 

The  Depth  of  the  Thread  should  be  a  little  greater  than  the  width  of 
the  finishing  tool,  in  order  to  give  the  necessary  clearance. 

Trying  the  Nut  on  the  Shaft.  —  Before  the  nut  is  tried  on,  about  two 
threads  should  be  turned  off  the  end  of  the  screw  (as  shown  on  the 
card)  and  the  burr  filed  off  the  tops  of  the  thread. 

73.  Knurling.  —  A  knurling  or  milling  tool  is  employed  to  make  in- 
dentations upon  cylindrical  surfaces,  which  are  required  to  be  turned  by 
hand  in  order  to  prevent  slipping.     Knurling  is  represented  on  the  card 
by  crossed  lines. 

Method  of  using  the  Double  Knurls.  — The  holder  is  placed  in  the  tool 
post  at  right  angles  to  the  surface  to  be  knurled,  and  the  two  hardened 
wheels  are  forced  against  the  work  with  considerable  pressure ;  the  car- 
riage is  then  slowly  traversed  along  the  work  unt'J  the  pyramidal  pro- 
jections produced  are  brought  to  a  point. 


A  -^  Ml  ""I  Hill  IIIUli 


